Due to a variety of factors including, but not limited to, global warming issues, fossil fuel availability and environmental impacts, crude oil price and availability issues, alternative energy sources are becoming more popular today. One such source of alternative and/or renewable energy is solar energy. One such way to collect solar energy is to use a solar receiver to focus and convert solar energy into a desired form (e.g., thermal energy or electrical energy). Thermal energy harvested from the sun is known in the art to be utilized in absorption heat pumps, domestic hot water and industrial processes, power generating cycles through the heating of a secondary heat transfer fluid, power generating cycles through the direct heating of power generating working fluid such as steam, and for heating. Furthermore, it is recognized that a wide range of energy consumers can be supplied via electrical and/or thermal energy such as air conditioning, refrigeration, heating, industrial processes, and domestic hot water. Given this, solar collectors that function in efficient manners are desirable.
Traditional thermal activated processes effectively consider every unit of energy into the system. Furthermore by definition solar energy is a function of solar intensity and thus at the minimum is absent during the nighttime, unless significant thermal storage is utilized that is currently very expensive. Additionally, it recognized in the art that vapor compressor heat pumps have coefficients of performance “COP” substantially higher than absorption heat pumps. And hot water heaters utilizing vapor compressor driven heat pumps also have substantially higher COPs as compared to direct heating of hot water having COPs less than unity. In addition, traditional solar collectors, particularly flat panel collectors, are temperature constrained due in large part to declining efficiencies as a function of temperature and the degradation of the working fluid which is often a mixture of a glycol and water. Solar collectors typically fall into the category of pump driven working fluid circulation or thermosiphon that respectively have the deficiency of requiring a pump or orientation of solar collector with respect to the “condenser”.
Heat pumps also have significant limitations that limit temperature including the requirement for oil lubrication that would suffer oxidative destruction at the higher temperatures desired within heat pumps. Additionally, the working fluid in virtually all refrigerants is significantly expandable across a wide operating temperature range.
The combined limitations of each individual component being the solar collector and the heat pump presents significant challenges that are further exasperated when high integration using the same working fluid for both devices is realized.